bio_add_page() and __bio_add_page() are capable of adding pages into bio, and now we have at least two such usages alreay: - __bio_iov_bvec_add_pages() - nvmet_bdev_execute_rw(). So update comments on these two helpers. The thing is a bit special for __bio_try_merge_page(), given the caller needs to know if the new added page is same with the last added page, then it isn't safe to pass multi-page in case that 'same_page' is true, so adds warning on potential misuse, and updates comment on __bio_try_merge_page(). Cc: linux-xfs@xxxxxxxxxxxxxxx Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- block/bio.c | 26 +++++++++++++++----------- 1 file changed, 15 insertions(+), 11 deletions(-) diff --git a/block/bio.c b/block/bio.c index 8d516d508ae3..07315056c2f6 100644 --- a/block/bio.c +++ b/block/bio.c @@ -662,6 +662,8 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, if (same_page && (vec_end_addr & PAGE_MASK) != page_addr) return false; + WARN_ON_ONCE(same_page && (len + off) > PAGE_SIZE); + return true; } @@ -781,9 +783,9 @@ EXPORT_SYMBOL(bio_add_pc_page); /** * __bio_try_merge_page - try appending data to an existing bvec. * @bio: destination bio - * @page: page to add + * @page: start page to add * @len: length of the data to add - * @off: offset of the data in @page + * @off: offset of the data relative to @page * @same_page: if %true only merge if the new data is in the same physical * page as the last segment of the bio. * @@ -791,6 +793,8 @@ EXPORT_SYMBOL(bio_add_pc_page); * a useful optimisation for file systems with a block size smaller than the * page size. * + * Warn if (@len, @off) crosses pages in case that @same_page is true. + * * Return %true on success or %false on failure. */ bool __bio_try_merge_page(struct bio *bio, struct page *page, @@ -813,11 +817,11 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page, EXPORT_SYMBOL_GPL(__bio_try_merge_page); /** - * __bio_add_page - add page to a bio in a new segment + * __bio_add_page - add page(s) to a bio in a new segment * @bio: destination bio - * @page: page to add - * @len: length of the data to add - * @off: offset of the data in @page + * @page: start page to add + * @len: length of the data to add, may cross pages + * @off: offset of the data relative to @page, may cross pages * * Add the data at @page + @off to @bio as a new bvec. The caller must ensure * that @bio has space for another bvec. @@ -840,13 +844,13 @@ void __bio_add_page(struct bio *bio, struct page *page, EXPORT_SYMBOL_GPL(__bio_add_page); /** - * bio_add_page - attempt to add page to bio + * bio_add_page - attempt to add page(s) to bio * @bio: destination bio - * @page: page to add - * @len: vec entry length - * @offset: vec entry offset + * @page: start page to add + * @len: vec entry length, may cross pages + * @offset: vec entry offset relative to @page, may cross pages * - * Attempt to add a page to the bio_vec maplist. This will only fail + * Attempt to add page(s) to the bio_vec maplist. This will only fail * if either bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio. */ int bio_add_page(struct bio *bio, struct page *page, -- 2.9.5
